How to fix issues with the "Back to Black" theme?
For some reason the devs of Blender have added this theme few versions earlier but haven't noticed that indeed edges in wire edit mode, grease pencil, empties,cameras and some other visible things in the 3d view are set to black, while the background color of the 3d view is black itself, which makes these objects impossible to see if not intersecting with the visible 3d grid if they are not selected (the ones which can be selected that is).

Solution is changing their colors in the User Preferences->Themes menu and then pressing "Save User Settings" so your own colors will remain when you restart Blender.
Blender devs should be notified of this. It's a good theme for people working at night but annoying and also difficult to newbies to fix yourself to make it usable.